Several studies have shown an increased incidence of
mitral valve disease in patients with Turner syndrome;
however, the study of Bondy et al.[
3] found that the
incidence of mitral valve disease was similar in Turner
syndrome patients compared to the overall population.
Supravalvular mitral ring has not been described in
patients with Turner syndrome. Supramitral ring rarely
occurs as an isolated lesion and is often accompanied
by other congenital heart diseases, including left-sided
obstructive heart lesions, such as the parachute mitral
valve, valvular and subvalvular aortic stenosis, bicuspid
aortic valve, and coarctation of the aorta. It frequently
presents as a part of Shone's complex. Supravalvular
mitral ring has been rarely reported as concomitant
with the Tetralogy of Fallot,[4] atrial septal defect, cor
triatriatum, left-sided superior vena cava, unroofed
coronary sinus, partial anomalous pulmonary venous
return, pulmonary venous obstruction, double orifice
mitral valve, transposition of the great arteries,
atrioventricular discordance, or double outlet right
ventricle.[5] Although cor triatriatum is a rare anomaly,
it can be encountered in all age groups and should
be considered in the differential diagnosis with
supramitral ring, as both anomalies are similar in
terms of clinical signs and symptoms.[6]
First described by Fisher[7] in 1902, SMR has been
the subject of several studies to better understand
the associated cardiac abnormalities. Collison et al.[8]
proposed that cardiac anomalies associated with SMR
could be classified into two main categories: SMR
associated with ventricular septal defect, and SMR
associated with left-sided obstructive pathologies,
particularly sub-aortic membrane, bicuspid aortic
valve, and coarctation of the aorta. In the first scenario,
it is important to rule out SMR in the context of
patients with ventricular septal defect and turbulence
across the mitral valve. In the second scenario, it has
been argued that supramitral ring should be excluded
in patients with multi-level left heart obstructions
to prevent residual defects.[8] In the light of these
findings, the lesions described for the second scenario
and the cardiovascular pathologies associated with
Turner syndrome show more overlap. The present
case had also a bicuspid aortic valve, but there was no
obstructive lesion requiring an intervention.
A study by Toscano et al.[9] described two different
variants of mitral ring, namely supramitral and
intramitral. It is of surgical significance to differentiate these two subtypes of mitral pathologies. Supramitral
ring is usually associated with a normal mitral valve
apparatus and can occur concomitantly with congenital
heart defects, as previously mentioned. Intramitral
ring is usually a part of the Shone's complex and is
associated with a normal subvalvular apparatus. The
intramitral ring can, therefore, be considered a subtype
of congenital mitral stenosis, characterized by varying
degrees of obstruction, both at the level of the ring
and the supravalvular apparatus. The supravalvular
type is a form of left atrial obstruction, whereas the
intravalvular type can be a part of an intrinsic mitral
pathology.
Resection of the supramitral ring is simpler and
more definitive, whereas intramitral ring resection
is more challenging. Although ring resection is
necessary, it is rarely sufficient, as the anatomy of
the subvalvular apparatus significantly contributes to
inflow obstruction. Satisfactory hemodynamic results
can be achieved through papillary muscle splitting and
correction of the interchordal space obliterations to
increase the effective mitral orifice. Commissurotomy
may postpone and avoid valve replacement. Ring
resection provides excellent long-term results in all
cases of supramitral ring and in half of the cases
of intramitral obstruction. Residual mitral stenosis
is present in the remaining half of patients with
intramitral obstruction. This condition is always
accompanied by an abnormal supravalvular apparatus
or valve hypoplasia, and follow-ups reveal moderateto-
advanced valve deficiencies, despite reoperation.
Predictors of poor surgical outcomes include mitral
annulus hypoplasia and abnormal supravalvular
apparatus. Moreover, being younger than one year of
age has been shown to be associated with poor surgical
outcomes.[9] In their study, Yildirim et al.[10] argued
that, even in patients with mitral annulus hypoplasia,
the stenosis gradient could be reduced to reasonable
values only with effective ring resection. Our case
had no major pathology related to the subvalvular
apparatus, and the existing interchordal obliterations
were corrected.
The morphology and optimal treatment of the
SMR are still controversial. Once detected, detailed
echocardiography should be performed considering
possible concomitant pathologies. In the presence of
suspicious findings, the diagnosis should be confirmed
with transesophageal echocardiography. A transseptal
surgical approach can achieve optimal resection of
the ring without causing mitral valve dysfunction, as was the case with the patient in the present report.
A transseptal surgical approach is also favorable, as it
facilitates the detection of concomitant pathologies.[8]
In conclusion, although rare, supramitral ring
should be considered in patients with Turner syndrome.
Concomitant pathologies must be carefully considered
before surgery. A transseptal surgical approach is
recommended. Simple resection is sufficient for isolated
lesions. Any concomitant mitral inflow obstruction
must be corrected simultaneously. Early results are
excellent for isolated defects.
Declaration of conflicting interests
The authors declared no conflicts of interest with respect
to the authorship and/or publication of this article.
Funding
The authors received no financial support for the research
and/or authorship of this article.